140] Quantitative Analysis of Oil Cakes 



93 



the ash is therefore liable to fuse. Should this take place 

 before all the carbonaceous matter has been burned off, the 

 liquid alkali will completely shut off the oxygen of the air by 

 coating the particles of charred substance. As a rule, an 

 Argand burner with the flame turned down low will be found 

 to burn the cake without any difficulty ; but the operation 

 must be watched carefully, especially if the cake in question 

 contain cotton seed. Decorticated cotton cakes give a very 

 fusible ash. Linseed cakes need no such precaution, and may 

 be ignited at a dull red heat. The residue is cooled and 

 weighed. It should be quite white. 



139. Sand. — Wash the ash out of the platinum dish 

 with a jet of dilute HC1 into a 4-oz. beaker. Add 10 c.c. of 

 strong HC1, digest on the water bath for ten minutes, filter, and 

 wash well with hot water. Transfer the filter without drying to 

 a platinum dish. Heat up very slowly over an Argand. When 

 perfectly dry, turn the light 

 up strongly and ignite until 

 the paper is thoroughly 

 burned. Cool and weigh. 



140. Oil. — The oil is 

 dissolved out from a 

 weighed quantity of the 

 cake by means of ether and 

 weighed after drying. This 

 is done by means of some 

 form of Soxhlet's fat ex- 

 tractor. Fig. 37 shows three 

 of these, the first of the 

 three being the most convenient, 

 tracted is wrapped in filter paper 

 tube, e. Ether is poured upon this until it rises to the level 

 of the top of the bent syphon tube, s. It then runs along 



Fig. 37. 



The substance to be ex 

 and placed in the wide 



